The invention relates to a can for preserving foodstuffs and a process for its manufacture, the body of which is basically cylindrical in shape and has a top and a bottom part permanently affixed to it.
Cans made from tin plate and used for preserving sterilizable foodstuffs over periods of several years have been known now for more than a century.
The metal tin, which provides the corrosion protection for the iron (steel) in tin plate, is one of the chemical elements which occurs in the Earth's crust in very small quantities. The relatively large amount of tin plate used for cans has now led to the situation where tin is already one of the metals giving problems as a result of its lack of abundance. Furthermore, it is also relatively expensive, for example four times as expensive as copper.
Aluminum, which is one of the most abundant elements in the Earth's crust, would be suitable for the manufacture of cans, if the aluminum sheet for this purpose had the same thickness as can material usually has, and would be therefore not significantly more expensive than the conventional cans made of tin plate. Certain plastics would also be suitable for the manufacture of cans, both with respect to mechanical properties and price. What is of disadvantage however in the case of plastic cans is that their physical and chemical structure is permeable to gases and aromas, which means that foodstuffs can not be stored unchanged in plastic cans for extended periods.
It has not been found that it is technically and economically feasible to make cans out of so-called aluminum-plastic composites and that these cans completely fulfil the requirements made of such cans both with respect to price and the preservation of foodstuffs.
The object of the present invention is to provide a can for the preservation of foodstuffs and a process for the manufacture of such cans by means of which the above mentioned disadvantages of the conventional cans are avoided.